Cloning a foal wasn't the focus of Hinrichs' research when she transferred five cloned embryos into mares. At the time, she was studying in vitro fertilization by intracytoplasmic sperm injection (ICSI), or injection of one sperm into an egg, in the laboratory. "We have been concentrating on in vitro culture of horse embryos, and what we can do to make that more efficient," she said. This research is directly applicable to making the cloning process more efficient as well."Nobody has worked out the best method to figure out how to grow a fertilized egg to an embryo in the laboratory," said Hinrichs, whose team has managed to get their ICSI success rate with blastocyst formation (embryos that are big enough to transfer to mares) to 20-35%. Procedures that manipulate the embryo in the laboratory increase the chances of early fetal loss or only trophoblast forming (a placenta without a fetus). Hinrichs wants to determine the best method for embryo culture, to optimize the number of pregnancies maintained and the number of mares that go to term and have a normal foal.During the ICSI studies, Hinrichs team decided to transfer five cloned embryos that were produced in the lab (which had resulted from more than 100 cloning procedures). Of those five, one resulted in the pregnancy that was lost.The Idaho/Utah team does their embryo transfer process differently than researchers at TAMU. When the Idaho/Utah team performs the cloning procedure, it immediately takes multiple cloned embryos and puts them into the oviducts of a recipient mare through a surgical incision (113 cloned embryos in 2003 resulted in three full-term mule colts). TAMU researchers perform the cloning procedure and wait to see which fertilized eggs become embryos in the laboratory, and then transfer the viable ones into the uteri of recipient mares through the cervix (non-surgically).
"We are planning to do more transfers of cloned embryos this year to determine the proportion of foals that go on to term successfully," said Hinrichs.When successful, would the cloning process become commercial for TAMU? "A lot of people approach you, but right now it's a very expensive procedure. Most people are interested in cloning, but not interested enough to fund research in it," she said.